Authors:
Nasour Bagheri
1
;
Babak Sadeghiyan
2
and
Majid Naderi
1
Affiliations:
1
Iran University of Science and Technology (IUST), Iran, Islamic Republic of
;
2
Amirkabir University of Technology Tehran, Iran, Islamic Republic of
Keyword(s):
Ring Hash Structure, Single Feedback Ring Hash, Multi Feedback Ring Hash, Hash function, Multi- collision Attack, Joux Attack, Preimage Attack, r-way collision.
Related
Ontology
Subjects/Areas/Topics:
Cryptographic Techniques and Key Management
;
Information and Systems Security
;
Public Key Crypto Applications
Abstract:
Ring hash structure is a new hash structure which has been introduced by Joux to strengthen the current hash structures against multi-collision attacks. In this paper, we present a cryptanalysis on Ring hash structure. We show that finding multi-collisions, i.e. 2k-way collision, for a Ring hash structure is not much harder than finding such
multi-collisions for ordinary MD hash structure. The complexity of our attack is approximately log (n) times harder than the complexity of attacks against MD structures. We employ these multi-collisions to find a D-way pre-image for this structure. We show the complexity of finding 2K-way multi-collision and 2k-way preimage are
O((k+1)x(n / 2)x2n/2 ) and O(kx n / 2x2n/2+2x2n ) respectively. We also show that Ring structure should not be used to create a hash function of 2n-bit length, by concatenatingmthis structure to any other hash structure of n-bit output length. We show that the time complexity of finding a collision for this concatenate
d structure is
O((k+1)x(n / 2)x 2n /2 )that is much smaller than Ω(2n ), which is expected for a generic-birthday attack.
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